1. Technical Field
The present invention generally relates to an ultrasound diagnostic device, and more particularly to an ultrasound diagnostic device including receiving data a transmission lines between scan line data forming units and channels. The present invention also relates to a method of forming the scan line data.
2. Background Art
Ultrasound signals transmitted from a transducer (an element) of ultrasound diagnostic device are reflected on a discontinuous surface of acoustic impedance, i.e., on a surface of a reflector in a target object. The transducer converts the reflected ultrasound signals into electric receiving signals. An ultrasound image showing an internal state of the target object is formed with the receiving signals.
To improve the resolution of the ultrasound image, a plurality of transducers is adopted, which are aligned in an array. In case of adopting a plurality of transducers, an outspread of the ultrasound signals can be effectively prevented and receiving sensitivity can be increased compared to the case of adopting a single transducer. Further, it is possible to focus the ultrasound beam electrically.
Focusing of the ultrasound beam includes a transmitting focusing and a receiving focusing. In the transmitting focusing, a transmitting order of the transducers is determined in consideration of the distance differences between the transducers and a focal point. The ultrasound signals transmitted from all the transducers, which participate in simultaneous transmitting, are simultaneously added at the same focal point in a phase. Thus, amplitudes of the transmitting ultrasound signals are at maximum at the focal point. In the receiving focusing, time delays are applied to the ultrasound signals reflected from the focal point so that the ultrasound signals have the same phase, as if the reflected ultrasound signals respectively arrive at the transducers at the same time.
With more focal points, a better resolution can be guaranteed. However, in forming an ultrasound image, the same signal processes should be performed repeatedly as many as the number of the focal points. Thus, the frame rate is decreased in proportion to the focal points. In order to solve this problem, a dynamic receiving focusing is introduced for a fine focusing. According to the dynamic focusing, the number of the receiving focal points increases, while the number of transmitting focal points is fixed. However, the improvement in the resolution is limited due to the fixed number of the transmitting focal points. U.S. Pat. No. 6,231,511 discloses an ultrasound signal focusing method and apparatus for forming data of a scan line by using all the transmitting beams of neighboring scan lines.
For improving a lateral resolution of the ultrasound image and a signal to noise ratio (SNR), it is preferable to transmit the receiving signals (RF data obtained from the receiving signals) provided by all of the transducers participating in one time of receiving (simultaneous receiving), namely, the receiving signals form a full aperture, to a signal focusing unit and a beam former, and to perform synthetic aperture imaging (SAI) with a full frame rate. However, to perform the SAI with the receiving signals from the full aperture, low resolution images (LRIs) of all the scan lines should be formed at the same time, and the LRIs are used to update high-resolution images (HRIs) previously formed. Thus, the receiving signals forming the full aperture should be used to form the respective scan lines, which require more complicated hardware (H/W).
In case of adopting “N” number of channels and “M” number of scan line data former, M×N number of data lines should be configured between the channels and the scan line data formers. Further, M number of RF buffers and accumulators for storing and updating scan line data are needed in consideration of the focusing delay and the apodization. For example, if N=M=128, then 16384 data lines are needed for connecting channels CH0 to CH7 and scan line data formers SC0 to SC7 according to a connection scheme shown in FIG. 1. It is not easy to configure the complicated connecting structure of FIG. 1 on a printed circuit board (PCB), although the semiconductor fabrication technique is being developed rapidly.